The High Pressure Ridge

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you. In this blog we’ll be discussing pressure during dry weather.

The High Pressure Ridge

In “The Rise of the Ridiculously Resilient Ridge,” the author points out that persistent high pressure in recent years led to extreme drought in California. In fact, the terminology, “Ridiculously Resilient Ridge” of atmospheric high pressure is frequently used to describe ‘the unusually persistent atmospheric anomaly responsible for redirecting winter storms over the Pacific and ultimately bringing record-breaking warmth and dryness to the Golden State.” But what amount of high pressure is occurring?

As shown in the figure below, a pressure of 45 mb above the middle atmospheric pressure (500mb geopotential height (GPH)) is attributed to be the cause of unusually persistent weather patterns. This level deflects storms that would bring rain and snow to ease drought conditions. With 1 bar = 1000 mb at sea level, 500  mb is near 5,500 meters (18,000 ft).

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The middle atmospheric pressure (500 mb geopotential height) anomaly (meters) for the Ridiculously Resilient Ridge, Oct-May 2012-2015. Source: The Rise of the Ridiculously Resilient Ridge

In contrast to the ridge that tends to bring warmer and drier weather, a trough is a lower pressure region that tends to bring in cooler and cloudier weather as it approaches. Both are analyzed on pressure surfaces aloft such as 850, 700, 500 and 300 mb.

In July 2016, according to the National Oceanic and Atmospheric Administration, a “heat dome” occurred over large portions of the United States. The websites states that “a heat dome occurs when high pressure in the upper atmosphere acts as a lid, preventing hot air from escaping.” This atmospheric occurrence forces air to sink back to the surface, warming the air even further on its way down.

The heat dome that resulted from the high pressure prompted the National Weather Service to issue heat alerts for more than a dozen states across the U.S.

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-Han Mai, Senior Marketing Specialist, All Sensors Corporation (